I'm not really sure about what really the cause of the drop on the coin price when it got listed in the market, but what i think, that would be because there are people who sell their coins in a lower price compared to the price when it firstly introduced during the ICO or something like that. because those people wanted to have quick money from the coins that they had. That is what i'm thinking of.
Sometimes, I do believe that it is also some of the mechanism put in place by the project developers too to avoid the coin being dumped by the general holdlers, since they own the larger part of the coins, what they do is to first of all dump the coin themselves so the price can crash a bit and discourage the investor or bounty hunter in further dumping as the price wont be a favorable ones for them pending the time the market picks up or pending when they have a working products because I have heard countless times that some of these ICO succeeded in raising funds without working products till after the ICO before they use the fund available to them to decide on one.